A new high-tech weather station will soon be installed near Eureka to better forecast damaging precipitation and flooding, like the drenching storm the North Coast recently witnessed.

In one five-day onslaught alone two weeks ago, some places in Humboldt County saw more than one foot of rain. Honeydew recorded 20 inches. Several low-lying areas around the county stayed underwater for several days.

The cause of these big storm events are atmospheric rivers, sometimes referred to as "Pineapple Express" storms because they're warm and occur when winds blow tropical moisture into narrow "filaments." The atmospheric rivers are themselves those concentrated filaments -- massive bands of water vapor that form over the ocean, each carrying as much as 10 to 20 Mississippi Rivers' worth of water. When the rivers hit land, they turn into intense, soaking storms, one on top of another.

"Invariably, when we have flooding, it's associated with an atmospheric river," said Mel Nordquist, science and operations officer at the National Weather Service Eureka office.

Eureka's atmospheric observatory -- the northernmost of four being installed along California's coastline -- will precisely measure the precipitation and flooding an atmospheric river could cause, Nordquist said. And, its location here could be more crucial than the other three observatories in predicting big storm events for the state.

An observatory at Bodega Bay will be installed this month. That installation will be followed by ones in Eureka, Point Sur, just south of Monterey, and Goleta, near Santa Barbara. All four are expected to be completed by 2014, according to the National Oceanic and Atmospheric Association website. Nordquist said the Eureka location will be installed in the next few months, but scientists from NOAA are still surveying and looking for the best location.

The four coastal observatories are the main component of a larger statewide observing network designed by NOAA, all with the goal of precise forecasting of atmospheric rivers. Ten snow-level radars will be installed in watersheds around the state, and a network of 43 soil moisture sensors are also being put in place statewide.

Nordquist said the Eureka location is crucial because atmospheric rivers often hit here first, then move south across California. A station here could pick up important warning information about the characteristics of the atmospheric river early on.

"It's kind of an early warning system here, in a way," he said.

High-tech instruments

A scientist from the NOAA office in Boulder, Colo., was in town Wednesday to survey different locations, including the Arcata/Eureka Airport, and the U.S. Coast Guard station on Humboldt Bay. Nordquist said they're currently leaning toward locating the observatory at the Samoa Airport.

The observatory itself will be 20 feet by 20 feet and run automatically, said Marty Ralph, chief of the Water Cycle Branch at the Earth System Research Lab, a division of NOAA in Boulder. Each of the four stations cost about $750,000, he said, and they are being funded by a California water infrastructure bond.

The observatory will have several weather-measuring tools that haven't been used extensively in Humboldt County.

One is the Radio Acoustic Sound System, or RASS. The system sends out a sonic burst of sound vertically; depending on how the sound waves return, meteorologists gain high-resolution, detailed information about lower parts of the atmosphere, about 6,000 to 8,000 feet up. That helps forecast fog and water vapor in the lower altitudes, Nordquist said. It can also see an atmospheric river, and it picks up detailed wind speed information.

In the summer, it can gather detailed information about bad air conditions, like smoke from a fire.

The problem is, the RASS is somewhat loud when it shoots out the sonic waves, so the station can't be located to close to a neighborhood or busy area, Nordquist said.

A GPS-based device will also be located at the station. It uses signals transmitted from satellites to measure moisture in the air -- again to help forecast atmospheric rivers, Nordquist said. The device creates an exact profile of moisture in the atmosphere.

"That's absolutely critical for forecasting," he said.

The weather-measuring instruments aren't new, Ralph said, but the way they're being specifically trained on atmospheric rivers is. And while the observatory will gather all sorts of other meteorological data, the main focus is atmospheric rivers because of their potential for major damage.

"Flooding events that affect California are primarily caused by atmospheric rivers that stall over an area," Ralph explained. He said the flooding can be worst when an atmospheric river hits on the heels of a previous storm, because waterways are full and soils are already saturated.

One of the old ways of collecting information on atmospheric rivers -- information the RASS will soon collect -- was from airplanes equipped with weather data-gathering devices. Nordquist said planes used to fly out of Murray Field near Eureka to collect that information. Or, other times -- and this practice is still used -- meteorologists send a balloon up through the lower atmospheric layers to collect information.

A more accurate forecast

Nordquist said the new observatory won't allow meteorologists to give a forecast any further in advance, but it will help draw more exact conclusions and detailed forecasts over the long haul.

"The better we understand the structures of these, it enables us to improve our forecasting techniques," he said.

The data from the new observatories will go to Michael Anderson and other scientists at the California Department of Water Resources. Anderson, a climatologist, said the stations will allow his team to "fine-tune" the forecast for the state. Then, his department will look at long-term trends, like whether storms are getting bigger or more frequent due to climate change.

USGS research hydrologist Michael Dettinger said he has been studying how climate change would affect atmospheric rivers, using seven different climate-change models. He said he's found that atmospheric rivers making landfall in Central and Northern California are likely to increase by 10 to 15 percent in the coming years.

"That is, on average, we project somewhat more atmospheric rivers (and somewhat larger ones) on average, but with some storms that are half again or twice as large as any in the historical period," Dettinger said in an email.

If that turns out to be the case, Ralph said it will be nice to have the observatories in place.

"Current atmospheric rivers are challenging enough," he said. "But I will say, as we learn how best to use this network -- if they do get worse -- we have some tools invented to help reduce the risks."